docs: def export(self, nidm_version, export_dir):
          """
          Create prov entities and activities.
          """
          # Create "Cluster Labels Map" entity
          self.add_attributes((
              (PROV['type'], self.type),
              (NIDM_IN_COORDINATE_SPACE, self.coord_space.id),
              (PROV['label'], self.label)
          ))